Jack is one of those men who I am sure always do best even in the most difficult situation

问题补充：

Jack is one of those men who I am sure always do best even in the most difficult

situations.

A. his

B. your

C. their

D. one’s

答案：

A. his

B. your

(答案→)C. their

D. one’s

解析：根据句意排除B，考查“do one’s best”的用法，Jack只是这么众多人中敢于面对困难的人之一，分析清楚句子前后关系可以判断C为正确答案。